FN Archimer Export Format
PT J
TI Origin and Evolution of the Fatu Kapa Magmatic System (North-Western Lau Back-arc Basin): Insight on the Genesis of High-Silica Lavas
BT 
AF Jeanvoine, Aurelien
   Chazot, Gilles
   Labanieh, Shasa
   Pelleter, Ewan
   Fouquet, Yves
AS 1:1,2;2:2;3:1,2;4:1;5:1;
FF 1:PDG-REM-GM-LCG;2:;3:PDG-REM-GM-LGM;4:PDG-REM-GM-LCG;5:PDG-REM-GM-LCG;
C1 Unité Géosciences Marines, Ifremer, Plouzané, GM, F-29280, France
   Laboratoire Géosciences Océan, Institut Universitaire Européen de la Mer (IUEM), Université de Brest (UBO), UMR 6538, Place Copernic, Plouzané, 29280, France
C2 IFREMER, FRANCE
   UBO, FRANCE
SI BREST
SE PDG-REM-GM-LCG
   PDG-REM-GM-LGM
UM LGO
IN WOS Ifremer UPR
   copubli-france
   copubli-univ-france
IF 4.371
TC 0
UR https://archimer.ifremer.fr/doc/00732/84397/89525.pdf
LA English
DT Article
CR FUTUNA 2 LEG1
   FUTUNA 2 LEG2
   FUTUNA 3
BO L'Atalante
DE ;contamination;felsic rocks;basalts;geochemistry;Lau basin
AB The South Eastern Futuna Volcanic Zone (SEFVZ; 50 km × 80 km) is located in the NW of the Lau back-arc basin at the northern boundary of the Futuna and YAO microplates. Fatu Kapa is an area (∼15 km × 10 km) of diffuse volcanic activity at the center of the SEFVZ and at the intersection of two volcanic axes with the Futuna fracture zone. At this place, the volcanic, tectonic, and hydrothermal activities are enhanced. The most differentiated volcanic series of the whole Futuna region are found in the Fatu Kapa area. Based on major and trace element data, four groups of volcanic rocks are distinguished in the Fatu Kapa area. The main groups form a well-defined transitional suite from basalts to andesitic and dacitic lavas that display enrichments in Zr, Cl and heavy rare earth elements. The most mafic lavas of this group are extracted from an Indian-type depleted mantle mixed with a component with trace element and isotopic characteristics similar to the nearby Samoa mantle plume. There is no evidence of subduction input. Petrological modelling shows that the mafic melts of the main group (Group 1A) evolve towards trachyandesites through fractional crystallization coupled with assimilation of 10 % of a Cl-rich and Th-poor melt generated by low-degree (≤2 %) partial melting of a hydrothermally altered basaltic crust. Rocks of Groups 1B(a) and 1B(b) were then generated by mixing of a mafic melt from Group 1A with a melt obtained by partial melting of andesitic and hydrothermally altered wallrock in shallow magma chambers. Extremely high Cl concentrations can be explained by assimilation of interstitial K- and Cl-rich brines in the pore water of the hydrothermally altered volcanic rocks before melting of these rocks. This is in good agreement with unusual extension of the Fatu Kapa hydrothermal area and indicates that, in the north of the Lau basin, the microplate boundaries are privileged zones to generate a complex felsic magmatism within areas of widespread hydrothermal alteration. Our study confirms the importance of assimilation and fractional crystallization and mixing processes in generating high-silica lavas in back-arc environments decoupled from subduction. 
PY 2021
PD SEP
SO Journal Of Petrology
SN 0022-3530
PU Oxford University Press (OUP)
VL 62
IS 9
UT 000708732900003
DI 10.1093/petrology/egab039
ID 84397
ER

EF